This disclosure is directed to a locking assembly, and in particular to a locking assembly including a locking mechanism for use in a prosthesis.
A prosthesis is a replacement limb comprised of a plurality of parts. The first component is a liner which is donned by a residual limb. The liner acts as a protective interface between a hard, weight bearing socket and the skin of the residual limb. Once the liner donned on the limb, the residual limb is received by the hard socket. The socket is made to specifically fit the residual limb. The hard socket for a transfemoral prosthesis (above-knee) has a component such as a knee joint connected to it. Below that is an aluminum or carbon fiber tube to which a foot module is connected. A transtibial prosthesis (below-knee) has the foot connected either directly to the hard socket or via a tube, depending on the amputee's height and the length of the residual limb.
Typically, an attachment pin is connected to the distal end of the liner, and engages a locking assembly that may or may not be laminated into the hard socket. The locking assembly is connected to the components connecting to the foot and effectively couples the liner, the hard socket and the components together.
Exemplary conventional locking assemblies are described in U.S. Pat. Nos. 5,507,837, 5,888,234, 6,106,559 and 6,605,118. Conventionally, the attachment pin has a plurality of rack-like notches that extend through a pin bore of a lock body of the locking assembly. The locking assembly is provided with a centering axle having a pinion gear at one end which engages with the notches of the attachment pin to draw the attachment pin into the lock body. The centering axle is mounted within the lock body so as to rotate in only one direction, and is further slidably mounted so as to disengage from the attachment pin upon axially movement within the lock body.
A problem inherent in the conventional locking assemblies is that the centering axle has a tendency to bind with the pinion gear upon wear of the prosthesis and due to the forces applied to the locking assembly by the weight of the user. Such binding of the centering axle with the attachment, in turn, makes it difficult for a user of the prosthesis to release the liner from the hard socket and components connecting to the foot.